Glosario

Abbe-Number

Also known as Abbe constant, it inversely quantifies the amount of dispersion in an optical medium. It is given by a function of the refractive index of a material at the f (486.1nm), d (587.6nm), and c (656.3nm) wavelengths. A material with a high Abbe number means that the different wavelengths will have nearly the same index of refraction in that medium, yielding less separation between wavelengths of light.

Aberration

Deviation from perfection in an optical system that results as a product of imperfect ray bending to form an image. Aberrations are inherent in all optical systems. Chromatic aberration, spherical aberration, coma, astigmatism, field curvature and distortion are the most commonly referred to aberrations.

Absorption

Light energy lost through transformation to another form, such as heat, while passing through a material.

Acceptance Angle

The maximum angle within which an optical fiber, electro-optic detector, or other component can collect light.

Achromatic Lens

Correction for primary chromatic aberration at two wavelengths. The simplest form is an achromatic doublet, consisting of two optical elements, a positive crown glass element and a negative flint glass element, cemented together.

Achromatic Objective

A type of microscope objective that has a flat field in approximately 65% of the center of the image, compared to the 80% of a Semi-Plan objective and the 95% of a Plan objective. They correct for chromatic aberration in the red and blue wavelengths and spherical aberration in the green wavelength.

Amplifiers

Analog Signal

A signal that continuously changes over time with respect to a reference level or standard. Analog-to-digital signal conversion involves sampling an analog signal at high frequency and representing each sample level by a number, stored as binary data. Analog cameras output analog video signals unlike digital cameras, in which case the analog-to-digital conversion takes place in the camera rather than in a computer.

Angle of Reflection

Angle Tolerance

The maximum angle between surfaces measured using an autocollimator assembly.

Angular Field of View (AFOV)

The angle of a lens’s view cone, typically specified as the full angle (in degrees) with respect to the horizontal sensor dimension. Used to determine FOV at a given working distance.

Anodization

The chemical oxidation of the surface of aluminum components to prevent corrosion and increase abrasion resistance. Black anodizing is not only cosmetically appealing, but also does not reflect light in optical, imaging and photonics systems.

Anti-Reflection (AR) Coating

A type of coating applied to optics designed to minimize reflections within an optical system and maximize throughout.

Aperture (f/#)

Also denoted by f-number (or f/#) and f-stop. In optics, it refers to the ratio of the focal length to diameter; whereas, in imaging, it refers to the ratio of the focal length to exit pupil of the system. A low f/# (fast lens) has high light collecting ability while a high f/# (slow lens) has low light light collecting ability.

Apochromatic

Correction for primary chromatic aberration at three wavelengths.

Argon-Ion Laser

A type of gas laser that uses argon ions as the amplification (lasing) medium. Although argon-ion lasers are generally larger and less efficient than Helium Neon (HeNe) lasers, they can be used to produce a wider variety of wavelengths.

Automatic Gain Control (AGC)

Average Extinction

When two polarizers are placed in front of a light source with transmission axes at 90 degrees to each other, the theoretical transmission should reach zero percent of the input. Because real polarizers will not reach this limit, average extinction is cited as a measure of how closely polarizers approach the theoretical limit.

Axial Illumination

Refers to light that strikes an object along the optical axis, typically introduced by a beamsplitter in front of the lens.

Axial Runout

For rotary stages, this is the amount of vertical motion of the stage as it rotates, measured with respect to the center of rotation.

Axicon

A conical prism, defined by its alpha and apex angles, that focuses a light source to a line consisting of multiple points along the optical axis. A beam generated by an axicon crosses the optical axis and forms a ring of increasing diameter over distance while maintaining a constant ring thickness.